1. Field of Invention
The present invention relates to a gas generator suitable for a restraining system for a vehicle.
2. Description of the Related Art
A gas generator for an air bag apparatus supplies a predetermined amount of gas to an airbag during activation. The amount of supplied gas is determined by the use of the airbag and specifications thereof. Therefore, a gas generator demonstrating a stable output is desired.
The amount of gas discharged per unit time from the gas generator is adjusted by a choke portion in a gas discharge path. The choke portion is the portion with the smallest cross-sectional area or opening area (minimum-area portion) in the discharge path to gas discharge ports. Therefore, it is necessary that the minimum-area portion be stably ensured at all times.
U.S. Pat. No. 5,941,563 discloses a partial view of a gas generator in which a diffuser 12 is attached to the end portion of a housing 14. The diffuser 12 has a ceiling portion 24, a side wall 22, and a bottom wall 26. The ceiling portion 24 is closed and a plurality of openings (slots 40) are formed in the side wall 22. Further, a single hole 28 is formed in the center of the bottom wall 26 and closed by a burst disk 34.
In this gas generator, the total opening area of the plurality of openings 40 is larger than the opening area of the hole 28 formed in the bottom wall 26 of the diffuser 12. Therefore, the hole 28 is the choke portion.
JP utility model registration publication JP-U No. 3129859 discloses a gas generator provided with an elongated cylindrical housing having a filter inside thereof, a combustion chamber charged therein with a gas generating agent to generate gas, a gas generating agent ignition device, and a gas discharge pipe mounted on the end portion of the housing on the filter side, wherein the cross-sectional surface area of the gas passageway opening in the gas discharge pipe is larger than the cross-sectional area of the intermediate section of the gas passage way (claim 1).
The cross-sectional area of the gas discharge pipe is described in detail in paragraph [0017], but the relationship with the total opening area of a plurality of gas discharge holes is not descried at all. Further, as described in paragraph [0021], the relationship of cross-sectional area described in paragraph [0017] is selected such that even the vicinity of the corners of the filter 4 on the gas discharge pipe 12 side can be used effectively as well.